Counterbalanced stair.



UNiTED sTATEs PETER L. LARSON, OF CHICAGO, ILLINOIS.

C-OUNTERBALANCED STAIR...

Specicationof Letters Patent.

ratented Jan. 5, 190e.

Application led Hay 2 5, 1908. -Serial No.'434=,964

To all whom it may concern:

Be it known that I, PETER L. LARsoN, a citizen of the United States, andresident of Chicago, county of Cook, and State of Iplli nois, haveinvented a certain neT and useful Improvement in Cor-.nterbalancedStairs, of

`which the following is a specification, and

which is illustrated in the accompanying drawings, forming apart hereof.

The invention relates to stairs adapted to turn about a horizontal pivotand, more particularly, to' those which are pivotally -seeired attheirupper end to the edge of .a

platform such as t at of the' balcony of a fire escape. In practicethese stairs are employed for connecting the balcony of afir'e escapewith the groundand in order that.

when not in use they may not provide a means of access to the buildingto which the fire escape is ap lied and may notv obstruct the assagewayelow, they are so counter- -Weig ted that they normally rest in 'asubstantially horizontal position, but are easily depressed to connectwith the ground by pressure aplplied to the treads of the stairs.

As usua y constructed the counterweights of these stairs take the formofan extension of the stair projecting beyond its pivot at the higherend. In order thaty this counter- Weight may clear the platform to theedge.

of which t stair is connected it is neces,- sarily applied to one sideonly/of thestair frame. n this construction t ere is a tendency of thatpart of the uncounterweighted weightedstair embodying the features ofthe invention; Fig. 2 showsvin side elevation a .-mimerals 10 an 11 in tdetail of the construction' separated from other parts; Fig. 3 is adetail transverse sectional view of the stair illustrated in Fig. 1;Fig. 4 is a lside elevation of the. stair illustrating the relativedisposition 'f its parts before being hung upon itspivotal support.

Figs. 5and 6 aredetail sectionalviews, andv taken on the lines 5-5 and'6-6 of Figs. V1`

and 3 respectively.- v

As shown, the. stair comprises side members which are enerall'designated by the fiedrawings. ,hese

-side members are connected by the treads generally designated 12.Preferably each of the side members comprises a pair of fparallel bars15 l-oneof which'is shown in 'detail in Fig. 2 of the drawings. The barsof each pair are connected adjacent .the higher end of the stair byplates 17, which are apertured to receive the pivotal support 18. iThepivotal support which is 'shown takes the form of a rod 18 projectinghori- Zontally from the Wall 19 of the building to which the stair isapplied. At the lower end of the stair thebars 15, 16 of eachpair areconnected by foot pieces 20. rI'he treads 12 may be of any convenientform of construction and as shown, each comprises a plurality ofparallel rods 2.1, each having its ends itted into cross pieces 22, 23and the treads are secured to the side members 10,

. 11 of the stair by securing the cross pieces f 22, 23 to the bars 15,16, of which the side members are composed, ,by bolts 24, as mostclearly shown in Figs. 3J and 6 of the drawings. j

Preferably the counter weight provided for normally supporting the stairin a substantially horizontal position, takes the form of a plurality ofweights 25. As shown', these weig its are fitted into' a channel member26 to which they are detachably secured by bolts 30. 'I he channelmember may be alpplied to one of the side members, as 10,;.of t e stairadjacent its higher end and extends beyon`d the pivot 18,'as shown at27. A secondchannel member 28 is secured to the channel y member 26adjacent its outer end for su porting additional counter weights 29. sthis counter weight is applied to but one 'of the side members, as 10,of the stair, there is a tendency for the free end of the uncounter-Weighted side member 11' to sag. Such a sagging would give the-stair adistorted and unsightly a pearance. In carrying out the invention, t isdistortion is prevented by so a plying the treads 12 to the side member10 tllfatbefore the stair is hung upon the pivotal 'support 18 andbefore the application of the, counter weights 25, 29. to the channelmembers 26, 28, the treads occu ya spiral rela# tion, as shown' in Fig.4 o the drawings. Most convenientl this spiral `relationof the` treadsis eHected y twisting each of the side members -land 11 aboutitslongitudinal axis 'before the` connection of the `treads thereto.

las

i ro

When each of the side members 10` andll .is formed ,from a pair of'bars125,116, y

Cir

- 3 of the drawings.

as'shown, this twisting of the 'side'members stair presents a distortedap earance when 1s en'ected by a twisting of the bars 15, .16 the partshave been assemble and mounted before their connection by the pivotplates 17 and foot pieces 2 0 tothe form illustrated in Fig. 2. In thenconnecting the treads 12 to the side members 10 and 11, the bars 15,

16 are strained byva drawing up of the bolts 24 to it snugly against theend pieces 22,23

of the treads and this straining of the bars 15 16 causes the end of theside member 11 to inclineupwardly towards .its outer free end, as shownin big. 4. Villen constructed in this AWay and hnng upon a rhorizontalpivot 18, the greater sagging of the outer free end of the side member11 ofthe stair than of the outer freeend of the member 10, because ofthe application of the cosnter Weights, 25, 29 to the channel bars 26,28 secured to the member 10, produces a suiiicient torsional strain inthe bars 15,' 16 of each of the side members 10 and 11 .to arrest thesagging when the parts have been broLght to the undistorted positionillustrated in 1* igs. 1 and If, however, from any chance, as by toogreat a twisting ofthe bars 15,' 16 of the side members 10 and 11, the

in the position of service, this distortion may be-corrected by atwisting of the stair as a Whole by grasping the outer free ends of thelside members 1 0 and 11 and by then ham.-

mering upon the twisted parts of the bars I claim as my invention Incombination, a stairI adapted to turn' about a horizontal pivotcomprising side members and treads connecting the -side members, and acounterweight applied to one side only of the stair, the treads of thestair being secured to the side member at the counterweiglited side ofthe'stair in spiral relation, Wliereby they are brought into parallelrelation by the torsional strain produced -in that side member by thetendency of that part of the nncounterweighted side of the stair remotefrom the pivot to sag.

PETER L. LARSON.

Witnesses:

CHARLES B. GILLsoN, LoUis K. GiLLsoN.

